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/** Mitt: Tiny (~200b) functional event emitter / pubsub.
* @name mitt
* @returns {Mitt}
*/
export default function mitt(all) {
// Arrays of event handlers, keyed by type
all = all || {};
// Get or create a named handler list
function list(type) {
let t = type.toLowerCase();
return all[t] || (all[t] = []);
}
return {
/** Register an event handler for the given type.
* @param {String} type Type of event to listen for, or `"*"` for all events
* @param {Function} handler Function to call in response to the given event
* @memberof mitt
*/
on(type, handler) {
list(type).push(handler);
},
/** Remove an event handler for the given type.
* @param {String} type Type of event to unregister `handler` from, or `"*"`
* @param {Function} handler Handler function to remove
* @memberof mitt
*/
off(type, handler) {
let e = list(type),
i = e.indexOf(handler);
if (~i) e.splice(i, 1);
},
/** Invoke all handlers for the given type.
* If present, `"*"` handlers are invoked prior to type-matched handlers.
* @param {String} type The event type to invoke
* @param {Any} [event] An event object, passed to each handler
* @memberof mitt
*/
emit(type, event) {
list('*').concat(list(type)).forEach( f => { f(event); });
}
};
}
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